The present invention relates to antiperspirant compositions that are water-in-oil emulsions, particularly clear gel compositions.
In U.S. Pat. No. 5,587,153 there is described clear gel antiperspirant compositions which are water-in-oil emulsions. The water phase includes a solubilized antiperspirant salt and the oil phase includes a silicone oil. Clarity is obtained by matching the refractive index of the two phases. These clear gel compositions cannot use conventional enhanced efficacy antiperspirant salts because such salts are unstable in aqueous solution and revert to non-enhanced form. Thus, the clear gel antiperspirant compositions do not achieve the highest possible antiperspirant efficacy. Nonetheless, the clear gel antiperspirant compositions marketed in the early 1990's achieved extraordinary commercial success.
In U.S. Pat. No. 5,925,338 there is described clear gel antiperspirant compositions with reduced fabric staining. These compositions are essentially identical to those described in the aforementioned '153 patent except that the non-volatile silicone oil has been reduced below about 5% and the compositions include a volatile linear silicone.
In U.S. Pat. No. 6,245,325 there is described enhanced efficacy antiperspirant salts which are stable in aqueous solution. These salts include a soluble calcium salt such as calcium chloride and a soluble amino acid such as glycine. Typically, these salts have a Ca:Al+Zr weight ratio of about 1:1 to about 1:28 and an amino acid:Al+Zr weight ratio of about 2:1 to about 1:20. Because these salts retain their enhanced efficacy in aqueous solution, they have an advantage over conventional enhanced efficacy salts which revert to the non-enhanced form in aqueous solution. For the sake of brevity, these salts are hereinafter identified as “CEAZCH” for calcium enhanced aluminum-zirconium chlorohydrate.
It had been hoped that the CEAZCH salts could be used to replace the conventional salts currently employed in the commercially marketed clear gel antiperspirant products in order to improve the antiperspirant efficacy of those products. Thus, in example 8 of the aforementioned '325 patent there is disclosed a clear gel antiperspirant composition containing CEAZCH. While this product had a higher efficacy than the commercially sold gel, the improvement in efficacy was not as high as desired. Moreover, the product had unacceptable application aesthetics, namely it produced unacceptable whitening and/or white clumps on the skin and hair. When it was attempted to reduce the whitening by addition of non-volatile emollient, this reduced the efficacy and exacerbated the formation of white clumps, rendering the product unacceptable.
It would be highly desirable to produce an emulsion antiperspirant composition, particularly a clear gel antiperspirant composition, with significantly improved antiperspirant efficacy over commercially available antiperspirant gel products. It would be particularly desirable to produce such a product that eliminated any undesirable application aesthetics, such as formation of white clumps on the skin and hair.